Transition metal catalysts are utilized for a wide variety of chemical reactions. As an example of the use of transition metal catalysts, commercial catalysts which have been employed in the conversion of gases into useful products have generally been composed of an iron-containing compound such as iron oxide which may be in the form of a magnetite. The iron oxide catalysts have been promoted in either a structural or chemical manner to enhance the stability of the catalyst, thus permitting the catalyst to be used in these reactions to obtain the desired products at an optimum value. One form of structural promotion of the iron-containing catalyst involves the addition of a component such as alumina which may be in various forms, such as alpha-alumina, eta-alumina, gamma-alumina, etc. to form a spinel structure with the magnetite to enhance and stabilize the catalyst possessing a high surface area. The addition of the promoter substance enhances the separation of the magnetite particles and thus will minimize any possible sintering effect which may occur during the reduction treatments as well as any sintering which may occur during the operation of the chemical reaction utilizing such catalysts. Another example of promoting the iron-containing catalyst is in a chemical manner such as the addition of an alkali material such as sodium oxide, potassium oxide, lithium oxide, barium oxide, magnesium oxide, etc. which, in essence, increases the basicity of the iron.
However, a disadvantage or drawback which occurs in many instances when utilizing a structural or chemical promoter is that an interaction develops between the structural and chemical promoter and the resulting combined aggregate separates and segregates from the iron catalyst, thus leading to an inhomogeneity in the distribution of the promoters with a concurrent loss in optimization of the catalyst activity. The loss of optimization further results in a decrease in the percentage of conversion of the gases with a corresponding decrease in the yield of the desired useable products.
As hereinbefore set forth, alkali compounds are known promoters of catalysts which may be employed in synthesis gas utilization processes such as a Fischer-Tropsch process, as well as being utilized in the synthesis of ammonia by reacting hydrogen and nitrogen at reaction conditions. As will hereinafter be shown, it has now been discovered that transition metal catalysts containing a structural promoter may be treated with a chemical promoter in such a manner so as to provide a more uniform promotion of transition metal catalysts.